This invention relates to brakes for bending sheet material, and in particular to a portable sheet bending brake for bending metal or plastic sheets such as are used in siding on homes and buildings.
Stationary brakes for making angular bends in sections of sheet metal generally employ a pair of jaws and a bending arm hinged to one of the jaws. Such brakes are operative to engage an extending section of the sheet metal work piece clamped between the jaws and have long been used in shops for forming sheet metal in various applications. In recent years smaller portable, lightweight brakes have been developed that may be used in the field by workmen to custom form sections of sheet metal in such applications as duct work in the home, aluminum siding for the home, etc. These brakes have typically employed a number of spaced C-shaped frame members joined together by rails. A fixed work clamping surface extends along one end of each of the frames, and a movable work clamping surface is supported on the other edge of the frames. The movable work clamping surface is moved toward and away from the fixed surface for clamping workpiece therebetween with one of the frame member arms.
The arms of the C-shaped frame members are movable with respect to each other by pivoting about a common point or are pivoted with respect to each other by some arrangement of linkage. These C-frame structures suffer from the disadvantage wherein after repeated use, the actuating mechanisms for the movable clamp wear and loosen. This results in misalignment between the bending edge of the movable clamp surface with respect to the bending member. The C-frame members are also relatively heavy, expensive to form, and susceptible to breakage at their throats. Additionally, the C-shaped members by reason of being spaced along the length of the brake limit the extent to which the workpiece can be extended through the back of the brake. The depth of the throat of the C-shaped section defines the limit of the workpiece extension.
Thus, it is desirable to have a brake wherein the workpiece can extend a significant distance through the back of the brake and more preferably wherein the back of the brake is unobstructed to provide the brake with optimum versatility. However, when C-shaped members are utilized, the only way to accomplish this is by utilizing C-shaped members having extremely long throats. As the length of the throat increases the propensity of the brake members to become misaligned or having the C-members fracture at the throat increases correspondingly.
Thus, there is a need within the industry for a portable brake wherein a workpiece can be extended through the back, yet be simple and sturdy to construct, with little propensity to become misaligned after repeated use.
One aspect of the present invention is a sheet bending brake assembly comprising a base with first and second ends. An anvil is supported in a vertically spaced distance from the base and is aligned with the base between the first and second ends. A hinge plate is mounted to the base and extends longitudinally between the first and second ends. A bending member is pivotally attached to the hinge plate for bending a workpiece clamped between the hinge plate and the anvil. The assembly is further characterized by a mechanism movably supporting the hinge plate and for moving the hinge plate toward the anvil to clamp the workpiece therebetween.
Another aspect of the present invention is a sheet bending brake for forming a workpiece wherein the brake comprises a base and an anvil having a bottom-clamping surface. The anvil is positioned in a fixed spaced relationship above the base and in combination with the base defines an unobstructed passage therebetween for receiving at least a portion of the workpiece. A movable plate is disposed between the base and the top plate wherein the movable plate is vertically translatable therein for clamping the workpiece between a top surface of the movable plate and the bottom clamping surface. A bending member is pivotally attached to the movable plate and extends longitudinally therealong for bending the clamped workpiece.
Yet another aspect of the present invention is a method of clamping an article of sheet material in a sheet bending brake wherein the sheet bending brake is of the type having a base and an anvil in a fixed space relationship above the base defining a passage therebetween. A movable plate is positioned in the passage and is vertically translatable therein, and a cam bar is interposed between the base and the movable plate wherein the movable plate and the cam bar have opposing cooperative cam surfaces. The method comprises the steps of placing the article of sheet material between the movable plate and the anvil and then translating the cam bar in a horizontal direction. The horizontal translation of the cam bar causes the opposing cam surfaces to translate one against the other thus causing the movable plate to rise as a result of the translation of the cam surfaces one against the other. Sufficient horizontal force is applied on the cam bar to firmly clamp the workpiece between the anvil and the movable plate.
The present invention provides a portable sheet bending brake that includes an open back to allow sheets of indefinite length to be formed.